To start a Guided Access session, follow these steps:
- Open the app you want to use.
- Triple-click the Home button.
- Adjust settings for the session, and then tap Start.
More info about setting up guided access. https://support.apple.com/en-us/HT202612
You also want to turn off the iPad sleep settings.
- Open the Settings app
- Go to "General" tab
- Click "Auto-Lock" and set to "Never"